1. Field of the invention
The present invention relates to a scanner, and more particularly, to a method for increasing the bit number of digital image signals generated by a scanner.
2. Description of the Prior Art
A common scanner comprises a scanning module for scanning a document and generating a plurality of corresponding analog image signals, and an A/D (analog to digital) converter for converting each of the analog image signals into a digital image signal with a bit number. The greater the bit number of the digital image signals outputted from the scanner is, the finer the reconstructed images will be. The bit number of the digital image signals generated by the scanner is often limited by the capacity of the scanning module and the A/D converter. For example, if the scanning module of a scanner can only output digital image signals with A bits, then it can only obtain digital image signals of A bits when scanning a document. In order to generate finer reconstructed images with increased subtlety, the scanner has to be equipped with a scanning module with a greater bit number which obviously would cost more money.
It is therefore a primary objective of the present invention to provide a transforming method for increasing bit number of digital image signals generated by a scanner to solve the above mentioned problems.
In a preferred embodiment, the present invention provides a transforming method for increasing bit number of digital image signals generated by a scanner, the scanner comprising:
a scanning module having a plurality of linearly arranged sensors for scanning a document and generating a plurality of corresponding analog image signals;
an A/D (analog to digital) converter for converting each of the analog image signals into a digital image signal with a first bit number; and
a white calibration area and a black calibration area for calibrating the scanning module;
the transforming method comprising:
(1) using the scanning module to scan the white and black calibration areas;
(2) generating a plurality of white and black analog image signals through scanning of the white and black calibration areas by each sensor of the scanning module, and generating a plurality of corresponding white and black digital image signals by converting the white and black analog image signals generated by each sensor through use of the A/D converter; and
(3) converting each digital image signal generated during scanning of the document by each sensor into a digital image signal with a second bit number according to the white and black digital image signals and a predetermined mapping method wherein the second bit number is greater than the first bit number.
It is an advantage of the present invention that finer and more colorful images are obtained through increasing bit number of digital image signals without increasing the cost of the scanner.
This and other objectives of the present invention will no doubt become obvious to those of ordinary skill in the art after having read the following detailed description of the preferred embodiment which is illustrated in the various figures and drawings.